TypeScript 5 Features You Should Actually Use

TypeScript 5 shipped with a lot of features. Here are the ones that actually matter for your daily work.

1. const Type Parameters

Before TS5, getting literal types required awkward workarounds:

typescript
// Before: Types get widened
function getRoutes<T extends readonly string[]>(routes: T) {
  return routes;
}
const routes = getRoutes(["home", "about"]); // string[]

// After: Use const modifier
function getRoutes<const T extends readonly string[]>(routes: T) {
  return routes;
}
const routes = getRoutes(["home", "about"]); // readonly ["home", "about"]

This is huge for type-safe routing, configuration objects, and constants.

2. Decorators (Finally Standardized)

typescript
function logged(target: any, context: ClassMethodDecoratorContext) {
  return function (...args: any[]) {
    console.log(`Calling ${String(context.name)}`);
    return target.apply(this, args);
  };
}

class UserService {
  @logged
  async getUser(id: string) {
    return db.users.find(id);
  }
}

No more experimentalDecorators flag needed.

3. satisfies + as const

The killer combo:

typescript
const config = {
  apiUrl: "https://api.example.com",
  timeout: 5000,
  retries: 3,
} as const satisfies Config;

// config.apiUrl is "https://api.example.com" (literal)
// But TypeScript still validates it matches Config

4. Improved Enums

typescript
enum Status {
  Pending = "pending",
  Active = "active",
  Closed = "closed",
}

// Now works correctly in unions
type StatusOrString = Status | string;

5. Better Bundle Size

TS5's new emit is 10-15% smaller. For large projects, this adds up.

Migration Tips

1. Update your tsconfig.json target to ES2022+
2. Remove experimentalDecorators if using new decorators
3. Review any code that relied on enum quirks

What I Skip

• Bundler resolution mode (too many edge cases)
• --verbatimModuleSyntax (breaks too many libraries)

Stick with the features that have clear benefits and minimal migration cost.